Bar code symbologies are widely used for data collection. Bar code symbols were originally developed to support numeric data entry. For example, the bar code symbologies known as UPC, EAN, Code 11 and Codabar are all bar code symbology standards which support only numeric characters, and a few special characters such as "+" and "-". The bar code standard Code 39 was the first alphanumeric bar code symbology standard developed. However, it was limited to 43 characters.
Code 93 is an improvement over Code 39. Code 93 is a continuous bar code symbology employing four element widths. An element is a single bar or a single space, thus in Code 93, each element may have one of four widths. Each Code 93 symbol has nine modules that may be either black or white (either a bar or a space). A module is the narrowest nominal width unit of measure in a bar code standard. Each symbol in the Code 93 standard contains three bars and three spaces (six elements), whose total length is nine modules long. Code 93, having nine modules and three bars per symbol is referred to in the industry as a (9,3) symbology. The Code 93 standard defines 48 unique symbols, and thus is able to define 47 characters in its character set plus a start/stop code. The 47 characters include the numeric characters 0-9, the alphabetic characters A-Z, some additional symbols and four shift codes.
The computer industry uses its own character encoding standards, namely, the American Standard Code for Information Interchange (ASCII). ASCII defines a character set containing 128 characters and symbols. Each character in ASCII is represented by a unique 7-bit code. Since Code 39 and Code 93 are limited to fewer than 50 characters, these standards are inadequate to uniquely represent each ASCII character. The four shift codes in Code 93, however, allow this standard to unambiguously represent all 128 ASCII characters. One drawback is that a series of two Code 93 symbols are required to represent a single ASCII character. Thus, bar code labels representing characters in the ASCII character set are twice as long as labels representing characters in the Code 93 character set.
New bar code symbology standards, such as Code 128, were developed to encode the complete ASCII character set, however, these standards suffer from certain shortcomings, including requiring shift codes or other preceding symbols to represent certain characters. All of these symbologies require increased processing time and overhead to process the entire ASCII character set.
The computer industry has grown beyond the limits of the ASCII character set. As the computer markets have grown, the need to support additional languages not defined by the ASCII character set has also arisen. New character sets were developed to accommodate clusters of characters in related languages. The original 7-bit ASCII character set was expanded to 8-bits thus providing an additional 128 characters or data values. This additional 128 set of data values (the "upper 128") allowed for additional characters present in the related romance languages (i.e., French, German, Spanish, etc.) to be represented.
As the computer markets grew internationally, however, even more languages were required to be included in the character set. Particularly, the Asian markets demanded a character set, usable on computers, which supported thousands of unique characters. To uniquely define each of these characters, a 16-bit encoding standard was required.
Several 16-bit encoding standards such as Unicode, JISC 6226-1983, and others have recently been developed. The Unicode character encoding standard is a fixed-length, uniform text and character encoding standard. The Unicode standard may contain up to 65,530 characters, and currently contains over 28,000 characters mapping onto the world's scripts, including Greek, Hebrew, Latin, Japanese, Chinese, Korean, and Taiwanese. The Unicode standard is modeled on the ASCII character set. Unicode character values are consistently 16 bits long, regardless of language, so no escape sequence or control code is required to specify any character in any language. Unicode character encoding treats symbols, alphabetic characters, and ideographic characters identically, so that they can be used in various computer applications simultaneously and with equal facility. Computer programs using Unicode character encoding to represent characters, but which do not display or print text, can remain unaltered when new scripts or characters are introduced.
New computer operating systems are beginning to support these comprehensive 16-bit code standards, e.g., WINDOWS NT.TM., manufactured by Microsoft Corporation of Redmond, Wash. The data collection industry, however, has failed to keep pace with the computer industry. No system currently exists for readily encoding the 16-bit computer character codes into bar code symbols. Therefore, there is a need to support these 16-bit computer character standards in the data collection industry, particularly for bar code symbologies.
Furthermore, most alphanumeric bar code symbologies are inefficient when used to encode a long series of numbers. When encoding a series of decimal numbers using Code 93 for example, the 26 bar code symbols reflecting the 26 alphabetic characters are not used. Therefore, there is a need to allow these alphanumeric bar code symbologies to more efficiently represent a long series of numbers.